Masks in hospital, don't work

Conclusions, Utilising a robust quasi-experimental approach,

we found no evidence that a mask policy significantly impacts the rate of nosocomial SARS-CoV-2 infection (with the Omicron variant)

Unmasking the mask: a time-series analysis of nosocomial COVID- 19 rates before and after removal

ECCMID 2023, abstract 5979

Reports and Proceedings

EUROPEAN SOCIETY OF CLINICAL MICROBIOLOGY AND INFECTIOUS DISEASES

B. Patterson , R. Mehra , A. Breathnach

St George's Hospital – London

Background

Mask wearing has been part of a package of infection control measures employed to reduce nosocomial COVID-19 throughout the pandemic.

A low-tech, low-cost intervention without well-established benefit was reasonable in the context of the early pandemic.

However, with a reduction in the severity of COVID-19 disease,

in later variants, the risk-benefit balance becomes more questionable.

Methods

Routinely collected infection control data

Nosocomial SARS-CoV-2 infection over a 40-week period

The intervention (study group)

Removal of a staff/visitor surgical mask-wearing policy,

for the majority of wards at week 26 of this period

Control group

Subset of specific wards retaining the mask policy

For both groups

Underlying community infection rate,

identified by unselected admission screening.

Omicron variant was the dominant strain throughout the period

Results for study group

In the context of a surge in SARS-CoV-2 infection,

removal of the mask policy was not associated with a statistically significant change in the rate of nosocomial SARSCoV-2 infection,

Incidence Rate Ratio (IRR) 1.11

and no post-intervention identifiable trend,

(to suggest a delayed effect)

IRR 1.01

Results for control group

No immediate change in infection rate

IRR 2.56

No delayed change in infection rate

IRR 1.08

Conclusions

Utilising a robust quasi-experimental approach,

we found no evidence that a mask policy significantly impacts the rate of nosocomial SARS-CoV-2 infection (with the Omicron variant)

While these data do not preclude a small effect,

the real-world benefit of this mitigation measure in isolation is likely to be modest within a healthcare setting.

Key messages

We are uncertain whether wearing masks or N95/P2 respirators helps to slow the spread of respiratory viruses based on the studies we assessed.

Hand hygiene programmes may help to slow the spread of respiratory viruses.

Authors' conclusions:

The pooled results of RCTs did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks.

Press coverage